1. Field of the Invention
The present invention relates to a starter motor electromagnetic switch which is attached to a starter motor, and which when energized, turns a shift lever and closes contacts in a circuit for the starter motor.
2. Discussion of Background
In FIG. 4, there is shown a cross sectional view of a conventional electromagnetic switch in an axial direction. Reference numeral 1 designates an excitation coil which is wound on a bobbin 2. Reference numeral 3 designates a fixed core which receives one end of the bobbin 2. Reference numeral 4 designates a yoke which forms a casing and is used for fixing the fixed core 3. Reference numeral 5 designates a plunger which is supported in an inner circumferential portion of a front end part of the yoke 4 so as to be movable in an axial direction, and which is made of a magnetic material and forms a movable core. Reference numeral 6 designates a return spring for the plunger 5. Reference numeral 7 designates a sleeve bearing which is staked to be fixed in a front portion of the plunger 5. Reference numeral 8 designates a hook which has a rear half portion inserted in a hole of the plunger 5 so as to be movably supported in an axial direction, which is made of e.g. a plastic material, and which has a front end portion engaged with an upper end portion of a fulcrumed shift lever (not shown) to turn it. Reference numeral 9 designates a compression spring for urging the hook 8 in a backward direction.
Reference numeral 10 designates a rod which is supported in a central hole of the fixed core 3 to be movable in an axial direction. Reference numeral 11 designates an insulation supporter which is fitted on the rod 10. Reference numeral 12 designates a movable contact which is fitted on the insulation supporter 11, and which is held by a retaining ring 14 through an insulation washer 13. Reference numeral 15 designates a compression spring which exerts an urging force on the movable contact 12. Reference numeral 16 designates an insulation cap which is pressed on a rear end of the fixed core 3 and crimped together by the yoke 4. Reference numeral 17 designates a pair of fixed contacts (only one is shown) which are opposed to the movable contact 12, with which a terminal bolt 18 is formed as one piece to extend outward, and which are connected to cables for a battery and the starter motor. Reference numeral 19 designates a return spring for the rod 10.
Reference numeral 20 designates a coil terminal which is formed in a strip shape, which has an inner end portion connected to lead wires 1a from the excitation coil 1, which has the inner end portion passed, with a small gap, through a guide hole 16b formed in a narrow shape in the insulation cap 16, and which has an outer end portion extended into a surrounding body 16a of the insulation cap 16. Reference numeral 21 designates a rubber plug which is fitted on the coil terminal 20, and which is seated on the bottom of the surrounding body 16a. As shown in the plan view of FIG. 5, the coil terminal 20 has a pinching portion 20a formed therein, the lead wires 1a being connected to the pinching portion 20a by pinching and soldering.
A coupler which is used to make plug-in connection with the coil terminal 20 is shown in part in section in the front view of FIG. 6. The coupler is indicated by reference numeral 22. Reference numeral 23 designates a cap which is made of a rubber material or the like. Reference numeral 24 designates a female connector which is arranged in the cap 23, which make solderless connection with a connection wire 25 from a key switch and so on, and which has a contact hole 24a formed therein to make the plug-in connection with the coil terminal 20.
Now, the operation of the conventional electromagnetic switch will be explained. When the excitation coil 1 is energized, the plunger 5 is attracted towards the fixed core 3. As a result, the hook 8 is retracted to turn the shift lever. Then, plunger 5 presses the rod 10, and the movable contact 12 closes the paired fixed contacts 17, causing the starter motor to start rotating.
Although the conventional electromagnetic switch as mentioned above has the coil terminal 20 supported by inserting it to the rubber plug 21, the conventional electromagnetic switch involves a problem wherein when great vibration is given from the side of an engine, the presence of the gap between the coil terminal 20 and the guide hole 16b of the insulation cap 16 causes the coil terminal 20 to undergo resonant vibrations, and the lead wires 1a connected to the coil terminal can be vibrated and cut off.